title: The transsulfuration pathway: a source of cysteine for glutathione in astrocytes.
abstract: Astrocyte cells require cysteine as a substrate for glutamate cysteine ligase (γ-glutamylcysteine synthase; EC 6.3.2.2) catalyst of the rate-limiting step of the γ-glutamylcycle leading to formation of glutathione (L: -γ-glutamyl-L: -cysteinyl-glycine; GSH). In both astrocytes and glioblastoma/astrocytoma cells, the majority of cysteine originates from reduction of cystine imported by the x                            (c)                                      (-)                          cystine-glutamate exchanger. However, the transsulfuration pathway, which supplies cysteine from the indispensable amino acid, methionine, has recently been identified as a significant contributor to GSH synthesis in astrocytes. The purpose of this review is to evaluate the importance of the transsulfuration pathway in these cells, particularly in the context of a reserve pathway that channels methionine towards cysteine when the demand for glutathione is high, or under conditions in which the supply of cystine by the x                            (c)                                      (-)                          exchanger may be compromised.
authors.affiliation: UCD School of Biomolecular and Biomedical Science, Conway Institute, University College, Dublin 4, Ireland. gethin.mcbean@ucd.ie
authors.forename: Gethin J
authors.initials: GJ
authors.lastname: McBean
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans
chemical_list: D005978:Glutathione; D003545:Cysteine